Transport.chem.dat FileTransport.chem.dat File
3 waters3 waters– Background, OBackground, O22 (solution 1) (solution 1)
– Sewage effluent, NHSewage effluent, NH44++ and Cl and Cl-- (solution 2) (solution 2)
– Rain ORain O22 (solution 3) (solution 3)
NHNH44++ oxidation oxidation
– SOLUTION 1 and 2 contain dissolved oxygenSOLUTION 1 and 2 contain dissolved oxygen
– SOLUTION 2 only NHSOLUTION 2 only NH44+ +
– NONO33- - produced where NHproduced where NH44
++ and O and O22 mix mix
NN2(aq)2(aq) and NO and NO22-- are disabled in .chem.dat are disabled in .chem.dat
Data to be written for Model ViewerData to be written for Model Viewer11
Changes for Solute TransportChanges for Solute Transport
1.1. Save As…Save As…2.2. Set solute transport and transient flowSet solute transport and transient flow3.3. Check dispersivitiesCheck dispersivities4.4. Check distribution of chemical conditionsCheck distribution of chemical conditions5.5. Initial head distributionInitial head distribution6.6. Check associated solutions of BCCheck associated solutions of BC7.7. Specify flux of sewage effluentSpecify flux of sewage effluent8.8. Set time step and simulation lengthSet time step and simulation length
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Transport Calculations Require Transport Calculations Require Dispersivity ParametersDispersivity Parameters
MEDIAMEDIA
Retain default of 1 m longitudinal Retain default of 1 m longitudinal and transverse dispersivityand transverse dispersivity
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Numerical Dispersion: Numerical Dispersion: Upstream-in-space, backward-in-timeUpstream-in-space, backward-in-time
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x
space
502
tv
time
Grid spacing is 500 mGrid spacing is 500 m
Velocity is 100 m/yr, 1 yr time stepVelocity is 100 m/yr, 1 yr time step
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IC: Set Chemical Initial ConditionsIC: Set Chemical Initial Conditions
Default CHEMISTRY_IC should have SOLUTION Default CHEMISTRY_IC should have SOLUTION
11
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IC: Use Steady-State Head Condition: IC: Use Steady-State Head Condition: flow.head.dat or ex5.head.200.datflow.head.dat or ex5.head.200.dat
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Flux: Sewage BedsFlux: Sewage Beds Draw an Draw an
arbitrary boxarbitrary box Flux Flux
boundaryboundary Flux scheduleFlux schedule
(next page)(next page) Solution 2 Solution 2 Z faceZ face
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Denis LeBlanc’s Flux Estimates (m/d)Denis LeBlanc’s Flux Estimates (m/d)
Beds 1-4 Beds 5-8 Beds 9-12 Beds 13-16 Beds 19-25
0 0 0 0 0 0
1936 -0.037 0 0 0 0
1941 -0.114 -0.114 -0.114 -0.114 -0.114
1946 -0.023 -0.023 -0.023 -0.023 -0.023
1956 -0.126 -0.126 -0.126 0 0
1971 -0.05 -0.05 -0.05 0 0
1978 -0.114 0 0 0 0
1984 0 -0.038 -0.038 0 0
1996 0 0 0 0 0
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Flux: Copy Zone for 4 More Sewage BedsFlux: Copy Zone for 4 More Sewage Beds
X 279725 to 279825X 279725 to 279825 Y 821500 to 821600Y 821500 to 821600 Z 0 to 20Z 0 to 20
Flux: Modify Box Zone for Sewage Beds 1-4Flux: Modify Box Zone for Sewage Beds 1-4
Click on zone in BC treeClick on zone in BC tree Ctrl-c, Ctrl-vCtrl-c, Ctrl-v Choose “specified flux”Choose “specified flux”
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Flux: Locations for Sewage BedsFlux: Locations for Sewage Beds
X min X max Y min Y max Z min Z max
Beds 1-4 279725 279825 821500 821600 0 20
Beds 5-8 279625 279725 821425 821525 0 20
Beds 9-12 279525 279625 821475 821575 0 20
Beds 13-16 279400 279500 821575 821675 0 20
Beds 19-25 279500 279600 821700 821800 0 20
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Set Print Frequencies for HDF FileSet Print Frequencies for HDF File
Double Click PRINT_FREQUENCYDouble Click PRINT_FREQUENCY
– Select years for HDF Select years for HDF chemistrychemistry
– Print every 2 yearsPrint every 2 years– Data to be written Data to be written
are selected in are selected in SELECTED_OUTPUT SELECTED_OUTPUT section of section of transport.chem.dattransport.chem.dat
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TIME: Set Time Step and Simulation LengthTIME: Set Time Step and Simulation Length
End time 1946End time 1946
Time step 1 yrTime step 1 yr
Start time 1936Start time 1936
Double Click TIME_CONTROLDouble Click TIME_CONTROL
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Visualize Results of Conservative TransportVisualize Results of Conservative Transport
– View P at 1946View P at 1946
– Show|SolidShow|Solid
– Show|Color BarShow|Color Bar
– Toolbox|Geometry—Z 20Toolbox|Geometry—Z 20
– Toolbox|Color BarToolbox|Color Bar 1e-10 min1e-10 min LogrithmicLogrithmic
– Toolbox|OverlayToolbox|Overlay
Model ViewerModel Viewer File|New—c:\student\CapeCodPhast\File|New—c:\student\CapeCodPhast\
transport.h5transport.h5
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View NHView NH44++, NO, NO33
--, and O, and O22
– Set to 1946Set to 1946 Toolbox|CropToolbox|Crop
– X min 0.45 X min 0.45 Ctrl-d changes Ctrl-d changes
viewview
Toolbox->Data N(5)Toolbox->Data N(5) Toolbox->AnimationToolbox->Animation
N(5) = NON(5) = NO33- - speciesspecies
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NHNH44++, NO, NO33
--, O, O22
NHNH44++ from effluent from effluent
NONO33-- from oxidation from oxidation
– Note faster flow at Note faster flow at toptop
OO22 consumed consumed
2222
To Decrease Numerical DispersionTo Decrease Numerical Dispersion
Refine resolution Refine resolution – Horizontal 250 mHorizontal 250 m– Vertical 2.5 m -20 to 20 mVertical 2.5 m -20 to 20 m– Time step 0.5 yrTime step 0.5 yr
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Refined GridRefined Grid Refined resolution Refined resolution
– Horizontal 250 mHorizontal 250 m– Vertical 2.5 m -20 Vertical 2.5 m -20
to 20 mto 20 m– 0.5 yr time step0.5 yr time step
Original resolution Original resolution – Horizontal 500 mHorizontal 500 m– Vertical 2.5 m -20 Vertical 2.5 m -20
to 20 mto 20 m– 1 yr time step1 yr time step
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SummarySummary Introduction PHAST for WindowsIntroduction PHAST for Windows Must always test numerical accuracyMust always test numerical accuracy
– Numerical dispersion for B-I-T, U-I-SNumerical dispersion for B-I-T, U-I-S– Oscillations for C-I-T, C-I-SOscillations for C-I-T, C-I-S
Cape CodCape Cod– Heads look goodHeads look good– Plume direction problematicPlume direction problematic– Tiny dispersivity is a killer, working on implicit Tiny dispersivity is a killer, working on implicit
TVD methodTVD method
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My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong
Start simple!Start simple! Add complexity sequentiallyAdd complexity sequentially
Check problem definition for completeness and correctnessCheck problem definition for completeness and correctness
– Properly posed problem that is physically realisticProperly posed problem that is physically realistic– Shape of regionShape of region– Spatial property distributions (Model Viewer, Spatial property distributions (Model Viewer, prefixprefix.O.probdef).O.probdef)
– Boundary condition distributions (Model Viewer, Boundary condition distributions (Model Viewer, prefixprefix.O.probdef).O.probdef)
– Initial conditions (Model Viewer, Initial conditions (Model Viewer, prefixprefix.O.head and .O.head and prefixprefix.O.comps).O.comps)
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My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong
Grid may be too coarse (GRID)Grid may be too coarse (GRID)– Numerical oscillation Numerical oscillation – Excessive numerical dispersionExcessive numerical dispersion
Time step may be too long (TIME_CONTROL)Time step may be too long (TIME_CONTROL)– Numerical oscillation Numerical oscillation – Excessive numerical dispersionExcessive numerical dispersion– Excessive operator splitting errorExcessive operator splitting error
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My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong
Check tolerance and controls on iterative Check tolerance and controls on iterative solver (SOLUTION_METHOD)solver (SOLUTION_METHOD)
Check controls on automatic time-step Check controls on automatic time-step algorithm for steady-state flow algorithm for steady-state flow (STEADY_FLOW)(STEADY_FLOW)
Review the simulation history Review the simulation history – Time steps (Time steps (prefixprefix.log).log)– Maximum changes in head (Maximum changes in head (prefixprefix.log).log)– Solver iterations (Solver iterations (prefixprefix.log).log)– Global balance tables (Global balance tables (prefixprefix.O.bal).O.bal)
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My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong
Use most robust numerics Use most robust numerics – Set backwards-in-time and upstream-in-Set backwards-in-time and upstream-in-
space differencing space differencing – Set equal dispersivities in all directionsSet equal dispersivities in all directions– No cross dispersionNo cross dispersion
Simplify the problemSimplify the problem– Flow onlyFlow only– Conservative transportConservative transport– Simplify the region and boundary conditionsSimplify the region and boundary conditions
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My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong
Look for errors in chemistryLook for errors in chemistry– Run batch chemistry in PHREEQCRun batch chemistry in PHREEQC– Run 1D transport in PHREEQCRun 1D transport in PHREEQC
Most problems with convergence in Most problems with convergence in chemistrychemistry– RedoxRedox– Small total concentration of element (~1e-14)Small total concentration of element (~1e-14)
Lack of chemical convergence may be the Lack of chemical convergence may be the result of a poor transport solution result of a poor transport solution (oscillations)(oscillations)
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My Model Doesn’t Work: What to My Model Doesn’t Work: What to do when things go wrongdo when things go wrong
Contact me Contact me [email protected]
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